UVA 1149 Bin Packing（装箱）（贪心）

题意：给定N(N<=10^5)个物品的重量Li，背包的容量M，同时要求每个背包最多装两个物品。求至少要多少个背包才能装下所有的物品。

分析：先排序，从最重的开始装，如果重量小于M，则如果能装一个重量最轻的，就再装一个重量最轻的，依此类推。

#pragma comment(linker, "/STACK:102400000, 102400000")
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cctype>
#include<cmath>
#include<iostream>
#include<sstream>
#include<iterator>
#include<algorithm>
#include<string>
#include<vector>
#include<set>
#include<map>
#include<stack>
#include<deque>
#include<queue>
#include<list>
#define Min(a, b) ((a < b) ? a : b)
#define Max(a, b) ((a < b) ? b : a)
typedef long long LL;
typedef unsigned long long ULL;
const int INT_INF = 0x3f3f3f3f;
const int INT_M_INF = 0x7f7f7f7f;
const LL LL_INF = 0x3f3f3f3f3f3f3f3f;
const LL LL_M_INF = 0x7f7f7f7f7f7f7f7f;
const int dr[] = {0, 0, -1, 1, -1, -1, 1, 1};
const int dc[] = {-1, 1, 0, 0, -1, 1, -1, 1};
const int MOD = 1e9 + 7;
const double pi = acos(-1.0);
const double eps = 1e-8;
const int MAXN = 1e5 + 10;
const int MAXT = 10000 + 10;
using namespace std;
int a[MAXN];
int main(){
    int T;
    scanf("%d", &T);
    while(T--){
        int n, l;
        scanf("%d%d", &n, &l);
        for(int i = 0; i < n; ++i){
            scanf("%d", &a[i]);
        }
        sort(a, a + n);
        int cnt = 0;
        int st = 0, et = n - 1;
        while(st <= et){
            if(a[et] <= l){
                if(st < et && a[et] + a[st] <= l){
                    ++st;
                }
                --et;
                ++cnt;
            }
        }
        printf("%d\n", cnt);
        if(T) printf("\n");
    }
    return 0;
}